Neuronal nitric oxide synthase (nNOS) catalyzes the oxidation of L-arginine to L-citrulline in the central nervous system, generating nitric oxide (NO), a critical neurotransmitter. Significant research has implicated the overexpression of nNOS—and overproduction of NO—in various neurological diseases, including Parkinson's, Alzheimer's, and Huntington's diseases, as well as neuronal damage due to stroke, cerebral palsy and migraine headaches. Inhibiting endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase (iNOS) is, however, undesirable, because these isozymes are responsible for maintaining crucial body function. Thus, selective inhibition of nNOS over its closely related isoforms, eNOS and iNOS, can provide a promising strategy in developing therapeutics for the treatment of neurodegenerative diseases.
Many organic scaffolds have been investigated over the past decade. Some compounds exhibit good potency and high selectivity, but suffer from poor bioavailability, thereby hampering their therapeutic potential. Yet other compounds, while promising, arc limited by synthetic challenge and/or low yield. As a result, there remains an on-going concern in the art to provide an efficient approach toward a facile synthesis of a wide range of such compounds, with structures optimized for enhanced pharmacological effect.